The present invention relates to a digital filter bank for frequency multiplex signals. Such digital filter banks are used to demultiplex and multiplex digitalized frequency multiplex signals. They are disclosed, for example, in an article of F. M. Gardner "On-Board Processing For Mobile Satellite Communications", published in Final Report: ESTEC Contract 5889/84, Palo Alto, Calif., Gardner Research Company, May 2, 1985, and in an article, entitled "Comprehensive Survey of Digital Transmultiplexing Methods," by Helmut Scheuermann and Heinz G/o/ ckler, in Proceedings of the IEEE 69 of November, 1981, at pages 1419-1450.
Among the drawbacks of known digital filter banks are that FFT (fast Fourier transformation) algorithms which are adapted for processing complex signals cannot be used to their best advantage.